Hey, I was going to reply to your post in the Unimelb questions thread but I'll just respond here.
Whilst I don't know how Calc 1 is like as a subject, but hearing that it's the majority of the Specialist Maths course in one semester I can imagine it's no slouch subject. From speaking to a friend doing Engineering through the Bcom who is 'forced' to do all of Calc 2, Lin Alg and Quantitative Methods 1, he finds the standard path to be much easier (perhaps biased because he's an Engineering student.)
Whether or not you have to love maths to get through it I can not say, this varies from person to person.
Also note that if you take the mathematics path, all of Calc 1, Calc 2 and Lin Alg will be credited as your level 1 breadths, meaning you can't take any other level 1 breadth subjects under the Bcom rules.
Check out this thread here:
Standard or Mathematics path for commerce? where Amity and I weigh up the two quantitative pathways. If you can not make a decision by enrolment period, I recommend taking both Calculus 1 and Quantitative Methods 1 in your 1st semester, so you can get a feel of how the subjects are run. This way you can make a decision about which path you want to do after your 1st semester.